In medical care, it is often necessary to infuse fluids into a patient through intravenous delivery (IV). These fluids can comprise, for example, nutritional fluids and drugs, such as antibiotics. In a common application, a primary container is provided which holds a volume of a primary fluid, such as a nutrient. A secondary container is also provided, containing a secondary fluid. The secondary fluid is commonly a drug or medicament.
Fluid flow lines extend from each of the containers to a Y-connection beneath the containers. A check valve or another one-way flow device is positioned in the flow line from the primary container between the primary container and Y-connection.
The secondary container is maintained at an elevation above the primary container. Therefore, the hydrostatic pressure of the secondary fluid is sufficient to close the check valve in the primary fluid flow line and block flow from the primary container until the secondary container is empty. When the secondary fluid has been infused, the check valve will open, permitting infusion of the primary fluid.
In the past, a number of techniques have been employed to control the rate of infusion of the primary and secondary fluids. Controlled drip chambers have been mounted on each container with the flow rate being calculated by the quantity of drops falling into the chamber per unit time. Positive pressure pumps have been used to pump the fluid from the containers to the patient. U.S. Pat. No. 4,265,240, issued May 5, 1981 to Jenkins discloses the use of two pumps, one in each fluid line, to infuse the fluids. Attempts have also been made to incorporate a flow control device in an IV delivery system operating by the hydrostatic pressure of the fluid. One device of this type is disclosed in U.S. Pat. No. 4,204,538, issued May 27, 1982 to Cannon. However, none of these devices have been totally effective.
In any IV delivery system, critical factors that must be recognized are the necessity to design the delivery system so that the system can be operated with a minimum of effort and training and the necessity to minimize opportunities for the operator to incorrectly set the infusion conditions. The nurse, or other operator, must be able to thoroughly understand the procedure to establish the desired flow. In addition, the procedure to set the desired flow rates should be designed to occupy the minimum of the nurse's time. Therefore, a delivery system is needed which permits the nurse to thoroughly understand the procedure for initiating and setting flow rates. A need exists also for a controller having a display which will be readily understood by operating personnel at all stages of operation of a delivery system for providing highly accurate flow control for a primary and a second fluid or, in an alternate mode of operation, a single fluid.